The present invention relates to a torsion spring system for a wheel suspension of a motor vehicle.
An example of such a suspension assembly is known from DE 10 2009 005 899A1. The suspension assembly includes a torsion spring bar which is actuatable by an actuator and extending in the vehicle transverse direction to about the vehicle transverse center and which on the wheel side acts on a driven lever that, in turn, is articulated to a wheel suspension element of the wheel suspension. The torsion spring bar is configured in the DE 10 2009 005 899A1 of several parts and in an interlaced arrangement in which two radially outer hollow bars and a radially inner solid bar are provided from spring steel, which are connected to one another in a force-transmitting manner via splines, for example.
In the torsion spring bar system known from DE 10 2009 005 899 A1, spring work is picked up and released during interplay of a wheel compression and wheel rebound motion. At the same time, it is possible that the actuator superimposes moments, i.e., to tighten or relax the torsion spring bars depending on need. The presence of the support spring as a primary spring, renders it possible for the rotary actuator to proportionally provide actuating forces to change the wheel load. A superimposition of the spring forces of the primary spring and the torsion spring bar continuously takes place, depending on the requirement of the driving situation and the corresponding command from the control. At the output of the torsion spring bar system is a rocker having an end to which a coupler is articulated. The coupler connects the rocker to the trapezoidal link, which is connected to the vehicle wheel. Thus, the torques generated in the rotary actuator can be transmitted via the load path motor/gear/torsion spring bar/rocker/coupler/trapezoidal link/vehicle wheel ultimately as linear actuating forces upon the vehicle wheel.
In the afore-described torsion spring bar system, the torsion spring bar is comprised of only two components, namely tube spring and solid bar spring. In contrast thereto, the remaining components are dimensioned absolutely rigid in the afore-mentioned load path without affecting the overall spring constant of the system. If there is need for example for realization of a softer torsion spring bar, as first measure the diameter of tube spring and/or solid bar spring would have to be reduced. However, by reducing the diameter, the operational capability of the torsion spring bar would decrease and at the same time stress would increase disproportionately, so that the tube spring and bar spring would have to be extended. Such a change in length is, however, not feasible in view of the extremely critical space conditions in the area of the wheel suspension. As a consequence, especially when smaller vehicle models are involved, which require a reduction in the total spring stiffness, such a rotary actuator cannot be installed because of the high packing tightness.
EP 2 01 1674 A1 discloses a two-part stabilizer for a motor vehicle, having stabilizer sections which are able to execute a rotational relative movement and to apply in the presence of a twisting load in opposite directions a restoring force which is adjustable by an actuator in conjunction with a gear. A torsion damper is provided in the gear. With the assistance of the torsion damper, gear noise can be avoided that otherwise would develop as a result of a tooth gap between the gear elements. The torsion damper reduces such mechanical noise within the gear, with the torsion damper being dimensioned such that the spring rate of the stabilizer assembly remains unaffected. This means that the spring rate of the stabilizer assembly is not lowered by the torsion damper,